In recent years, development of an optical disc as a recording medium of a large capacity has been progressed. For example, a CD (Compact Disc) on which music information has been recorded, a CD-ROM in which data for a computer is recorded, a DVD (Digital Versatile Disc or Digital Video Disc) which handles video information, and the like are known.
The optical discs mentioned here are read only discs. In recent years, an optical disc on which data can be additionally written once or data can be rewritten like a CD-R (CD-Recordable) disc, a CD-RW (CD-Rewritable) disc, or the like has been put into practical use. Further, development of various optical discs such as double density CD whose recording capacity is increased while keeping a shape similar to that of a CD, CD2 in which an affinity of both of an ordinary CD player and a personal computer can be enhanced, and the like has been progressed.
The optical disc of CD2 has an area on the inner rim side and an area on the outer rim side. In the area on the inner rim side, for example, audio data has been recorded in a format similar to that of an ordinary CD-DA (CD digital Audio) so that it can be also reproduced by the ordinary CD player. In the area on the outer rim side, in order to realize an affinity with the personal computer, contents data is filed and recorded on the basis of the specification of the CD-ROM.
A method of recording contents data of a multimedia comprising the audio data and image data onto such an optical disc of CD2 in accordance with the specification of MPEG2-PS is considered. As a compression system of the audio data, for example, use of ATRAC3, MP3, or AAC is considered.
As a compression system of the audio data, there are known: a subband system in which the inputted audio data in the time base direction is divided into a plurality of bands by a band dividing filter and compression encoded; a transform encoding system in which the inputted audio data in the time base direction is transformed into data in the frequency base direction by an orthogonal function such as a DCT or the like and compression encoded; and a hybrid system in which both of those systems are combined. ATRAC3, MP3, or AAC is an audio compression system which belongs to the hybrid system. The audio data cut out by a predetermined time window is band divided and MDCT transformed, so that the compression encoding is executed.
For example, in ATRAC3, the audio data whose sampling frequency is equal to, for instance, 44.1 kHz is cut out by a time window of, for instance, 11.6 msec and encoded by the hybrid system. In the time window of 11.6 msec, the audio data of 512 samples is cut out. Assuming that one sample consists of 16 bits, the encoding is executed every 2048 bytes. In ATRAC3, since adaptive bit allocation is performed, it is possible to arbitrarily cope with a bit rate. When a transmission bit rate is equal to 66 kbps, one encode unit is compressed to 192 bytes. When the transmission bit rate is equal to 105 kbps, one encode unit is compressed to 304 bytes. When the transmission bit rate is equal to 132 kbps, one encode unit is compressed to 384 bytes.
In CD-ROM Mode-1, a subcode block consisting of 98 frames is set to a sector and data is recorded on a sector unit basis. A size of one sector is equal to 2352 bytes and a data recording capacity among them is equal to 2048 bytes. In the case of recording the contents data by MPEG2-PS, data of one pack and one packet is recorded in one sector. For example, assuming that a pack header of 14 bytes is added and a packet header of 14 bytes is added, a data capacity of the contents which can be recorded in one sector is equal to 2020 bytes.
As mentioned above, in the specification of CD-ROM Mode-1, a data capacity of one sector is equal to 2048 bytes. When the data of MPEG2-PS is recorded, assuming that the pack header of 14 bytes and the packet header of 14 bytes are added, a data capacity of the contents which can be recorded in one sector is equal to 2020 bytes.
On the other hand, for example, in the audio data compressed by ATRAC3 of a bit rate of 105 kbps, a size of one encode unit is equal to 304 bytes.
As mentioned above, the data capacity of the contents which can be recorded in one sector and the size of one encode unit are independently predetermined. The invention is not limited to the case of ATRAC3, but in MP3 or AAC as well, the data capacity of the contents which can be recorded in one sector and the size of one encode unit are independent. Therefore, if encode units are continuously recorded, an encode unit which is data-recorded over two sectors is caused.
For example, if the audio data in which the size of encode unit is equal to 304 bytes (ATRAC3 of the bit rate of 105 kbps) is recorded into the capacity of one sector of 2020 bytes, the number of encode units which are arranged in one sector is equal to2020/304=6.64Although six encode units can be completely arranged in one sector, the seventh encode unit is recorded over a part of the next sector.
If the encode unit which is recorded over the sectors is caused as mentioned above, a head of the encode unit becomes unclear upon accessing and a problem such that in a fast-forward mode, a fast-rewinding mode, or a search mode, it is difficult to access a desired sector and encode the data occurs.
That is, in the case where the data is recorded by the specification of CD-ROM Mode-1, the access is executed on a sector unit basis. Even if the encode unit has been recorded over the sectors, so long as the continuous reproduction is executed, the data of such an encode unit is continuously reproduced from the two adjacent sectors, so that there is no problem.
However, when the user intends to access the desired sector and start the reproduction in the fast-forward mode, fast-rewinding mode, search mode, or the like, if the encode unit has been recorded over the sectors, the complete encode unit cannot be obtained in the head portion of the sector and such an encode unit cannot be decoded. In such a case, therefore, it is necessary to skip to the next complete encode unit and start the decoding from a position where the complete encode unit can be reproduced.
However, particularly, in ATRAC3, unlike MP3 or AAC, since a header showing the head of the encode unit does not exist, it is difficult to find the next complete encode unit.
A method whereby the head of the sector is always made coincident with the head of the encode unit is, therefore, considered. For example, as mentioned above, in the case of recording the audio data in which a size of encode unit is equal to 304 bytes and which has been compressed by ATRAC3 of the bit rate of 105 kbps, a method whereby six encode units per sector are recorded from the head of the sector and residual sectors are stuffed is considered. As mentioned above, if the head of the sector and the head of the encode unit coincide, the desired sector is accessed and, when the head of the sector is accessed, the decoding is performed from the head of the data of such a sector, so that the data can be reproduced. In this case, however, a waste occurs in the data capacity of2020−304×6=196 bytesper sector.
It is, therefore, an object of the invention to provide data recording method and apparatus, data reproducing method and apparatus, and a data recording medium, in which even when accessing on a sector unit basis, data can be certainly reproduced from the head of an encode unit and a data capacity does not to waste.
Another object of the invention is to provide data editing method and apparatus, in which even if data is edited, the data can be certainly reproduced from a head of an encode unit at an edit point and a data capacity does not go to waste.